Wear compensating apparatus including bi-directional spring clutch



Dec. 21, 1965 R. F. HANFT 3,224,545

WEAR COMPENSATING APPARATUS INCLUDING BI-DIRECTIONAL SPRING CLUTCH Filed Jan. 30, 1964 2 Sheets-Sheet l FIG.1

I INVENTOR. ROY F. HANFT Dec. 21, 1965 R. F. HANFT 3,224,545

WEAR COMPENSATING APPARATUS INCLUDING BI-DIRECTIONAL SPRING CLUTCH 2 Sheets-Sheet 2 Filed Jan. 30. 1964 FIG.3

United States Patent 3,224,545 WEAR COMPENSATING APPARATUS INLUDING BI-DHRECTIONAL SPRING CLUTCH Roy Hanft, Lexington, Ky., assiguor to International Business Machines Corporation, New York, N.Y., a

corporation of New York Filed Jan. 30, 1964, Ser. No. 341,244 3 Claims. ((31. 197-16) The present invention relates generally to the mechanical arts and more particularly to apparatus which automatically compensates for wear in mechanisms that move a driven member to different positions, such as the mechanims employed to move a print element of a typewriter.

In U.S. Patent 2,919,002, issued to L. E. Palmer and which is assigned to the assignee of the present invention, there is shown a typewriter having a single print element that is movable to different positions for bringing any one of various characters to a printing position. The print element has the general shape of a truncated spheroid and the mechanisms for moving the print element comprise means for rotating the print element in either direction from a home position. A detenting means, such as the type disclosed in U.S. Patent 2,926,768, issued to L. E. Palmer et a1. and which is also assigned to the assignee of the present invention, is employed for accurately locating the print element in each of its printing positions. This detenting means will compensate for slight inaccuracies in adjustment of the mechanisms for moving the print element and for slight wear in their operating parts. If nothing more is provided, a manual adjustment of the mechanisms becomes necessary as soon as the inaccuracies in the mechanisms and the wear in their operating parts exceed the compensation that may be obtained from the detenting means.

The above problem has been recognized in the art and it has previously been proposed to provide a wear compensating device which will automatically compensate for a portion of the wear in the mechanisms to obtain a longer period of operation before manual adjustment is necessary. Such a device, as shown in U.S. Patent 2,989,166, issued to G. A. Walker et al. and assigned to the assignee of the present invention, comprises a pair of arms carrying a pulley about which the tape passes. One end of the tape is connected to a pulley fixed on a spindle carrying the print element. A spring tends to rotate the latter pulley for maintaining a tension on the tape. Formed in the arms are vertical slots carrying a roller which is held against a lever by the action of the tape on the arms. During compensation action, the lever is caused to move slightly relative to the arms and their permits the roller to move to a lower position in the slots. If the tension on the tape is inadvertently removed at any time, the arms may move relative to the lever and permit the roller to drop, thereby causing the setting of the device to become inaccurate. A removal of the tension on the tape may take place in many ways, such as when the print element is being removed or replaced from the spindle by the typist. By providing a clamping member which is held by a spring against the roller at all times except when the compensating device is in a position to make an error correction, an inadvertent movement of the roller in the slots is prevented. This latter arrangement is disclosed in U.S. Patent 3,133,620, issued to S. A. Okcuoglu et a1. and which is also assigned to the assignee of the present invention.

The above described wear compensating device has been found well adapted for the purposes intended and has been extensively employed. However, it is desirable to compensate for a greater portion of the inaccuracies or wear in the mechanisms or parts, such as at least a portion of the wear in the case shift mechanism operating on the tape and changes in the effective length of the tape itself. Further, the wear compensating apparatus should be relatively simple in construction and operation, being formed from a small number of uncomplicated parts.

Briefly, the present invention relates to improved wear compensating apparatus comprising a spring clutch means interconnecting a driven member and a rotatable member. The spring clutch is biased in such a manner that the driven and movable members move together. However, when at least one preselected position is reached, the tensioning or biasing forces are removed from the spring clutch and the driven member moves independently of the movable member under the action of a helper spring or the like. The relative independent movement continues until the wear in the mechanisms occurring during the selection operation are compensated. The driven member comprises a rotate pulley while the movable member is a hub which is directly connected to a print element.

It is the primary or ultimate object of the invention to provide improved wear compensating apparatus which automatically adjusts itself to compensate for at least a portion of the wear in the mechanisms employed for moving a driven member to different positions.

Another object of the invention is the provision of wear compensating apparatus which is effective to automatically compensate for a greater portion of the wear in the mechanisms employed to rotate a print element of a typewriter than it has heretofore been possible to automatically compensate. The wear compensating apparatus is located at the base of the spindle mounting the print element whereby a greater portion of inaccuracies and wear in the various mechanisms acting on or guiding the tape or changes in the effective length of the tape are compensated. A significantly longer period of typewriter operation is obtained before manual adjustment is necessary.

A further object of the invention is the provision of wear compensating apparatus having the characteristics set forth above which is extremely compact and of simplified construction whereby the same can be manufactured at a low cost but yet is very rugged and highly reliable in operation.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings.

In the drawings:

FIGURE 1 is a front view of printing mechanism embodying improved wear compensating apparatus constructed and operated in accordance with the teachings of the present invention;

FIGURE 2 is a perspective view of a print element and means for rotating it from a home position; and

FIGURE 3 is an end sectional view taken along the section line 33 of FIGURE 2.

Referring now to the drawings, there is shown printing mechanism of the type disclosed in U.S. Patent 2,919,002, mentioned above, except for the wear compensating apparatus generally designated by the reference numeral 10. Those desiring a more detailed description of the overall printing mechanism than is hereinafter set forth should refer to this patent and the IBM Customer Engineering Series 72 Instruction Manual, copyright 1961 and published by International Business Machines Corporation, 590 Madison Avenue, New York 22, New York.

A print element 11 having the general shape of a truncated spheroid is detachably and removablly secured to the upper end of a spindle 12. Formed about the periphery of the print element 11 in generally vertically spaced and circumferentially extending rows are a plurality of characters 13. Mechanisms are provided for rotating and tilting the print element 11 to bring any selected character to a printing position in front of a printing platen 14. The print element is then thrown forward toward the printing platen 14 to effect printing of the selected character.

The spindle 12 is mounted for rotation in either direction on a rocker plate 16. As most clearly shown in FIG- URE 3 of the drawings, an annular spring arbor 17 is rigidly attached to the lower end of the spindle 12 by set screw 18 or other convenient attachment means. A spring clutch 19 has a lower end portion 20 which nestingly receives a portion of the spring arbor 17. An upper end portion 21 of the spring clutch 20 nestingly receives a depending annular hub 23 of a rotate pulley 24. The rotate pulley 24 is mounted for rotation with respect to the spindle 12 and has a relatively large diameter with a groove 25 formed about its outer periphery.

Mounted from the rocker plate 16 is a generally cupshaped spring cage 26 that receives a coil spring 27 of the mainspring type. The outer end of the coil spring 27 is attached to the spring cage 26 while the inner end is connected to spring arbor 17. The convolutions of the coil spring 27 are wound in such a direction and to such an extent that the spring arbor 17 is biased for rotation in a clockwise direction as indicated by the arrow 28 regardless of the amount and direction of rotation of the spindle 12 and print element 11 during a character selection or case shift operation. As will be hereinafter more fully explained, the convolutions of the spring clutch 19 are of such a diameter and wound in such a direction to provide a drive connection between the rotate pulley 24 and the spring arbor 17 except during the interval when a wear compensating adjustment is made.

Firmly secured to the rotate pulley 24 by any convenient clamping means is one end of a thin and flexible rotate tape 30. The rotate tape 30 is received in the peripheral groove 25 of the rotate pulley 24 and, after making slightly less than two complete revolutions of the rotate pulley, extends longitudinally to a pulley 31 rotatably mounted at the upper end of a rotate arm 32. The rotate arm 32 is located at the left side of the printing mecha nism as viewed in FIGURES l and 2 of the drawings. After passing about the pulley 31, the rotate tape 30 extends longitudinally across the printing mechanism to a case shift pulley 33 mounted for rotation on the upper end of a case shift lever 34. Case shift lever 34 is located at the right side of the printing mechanism. The other end of the rotate tape 30 is connected to a stud 35 which extends from a carrier 36.

The carrier 36 (see FIGURE 1 of the drawings) is guided for longitudinal movement in front of the printing platen 14. Escapement and carriage return apparatus, not shown, are provided to cause longitudinal movement of the carriage. The rocker plate 16 is pivoted to the carrier 36 by rocker shaft 37 so that the rocker plate 16 and the print element 11 can be thrown forward by print apparatus, not shown, to effect printing. The mounting of rotate tape 30 is such that as long as the rotate arm 32 and case shift arm 33 remain in fixed positions, the print element 11 will retain the same rotational position regardless of the longitudinal position of the carrier 36, rocker plate 16 and the print element 11 with respect to the printing platen 14. However, movement of either the rotate arm 32 or the case shift arm 34 will cause rotational movement of the print element.

The rotate arm 32 is pivotally mounted intermediate its ends by pin 40 and is connected at its lower end to a rotate link 41. The other end of rotate link 41 is attached to one arm of a rotate bellcrank 42 which is supported at 43 and Wh se ther a m is connected to a balance lever 4. 44 forming part of rotate selection mechanism generally designated by reference numeral 45. Included in the rotate selection mechanism are selecting links 46 and 47 which are hook shaped at their lower ends and are connected at their upper ends to a floating member 48 in such a way they may swing forwardly relative to the floating member and also permit pivotal movement about the latter in either direction. A link 49 pivotally connects floating member 48 to one end of another floating member 50 which is connected by a link 51 to one end of balance lever 44. Another selecting link 52 is connected to the opposite end of floating member 50 and has a hook shaped portion at its lower end. The other end of balance lever 44 is pivotally connected to a link 53 which is normally held in the position shown but may be moved vertically a predetermined distance to a higher position.

During a character selection operation, one or more of the selecting links 46, 47 and 52 are swung forwardly to position their hooked portions under a bail 54 which is caused to rock downwardly. The connections between the floating members 48 and 50 and the links 49 and 51 are such that a movement of the selecting link 46 downwardly with the bail 54 causes the rotate bellcrank 42 to rotate one unit in a counterclockwise direction. Movement of either selecting link 47 or selecting link 52 downwardly with the bail 54 causes the bellcrank 42 to rotate two units in a counterclockwise direction. When two or more selecting links are moved with the bail, the rotate bellcrank rocks a distance equal to the sum of the distances obtained by movement of the individual selecting links. As the rotate belicrank 42 rocks counterclockwise, the rotate arm 32 pivots counterclockwise and pulley 31 pulls on the tape 30 to cause a rotation of the print element 11 in a counterclockwise direction. A rocking of the bellcrank 42 one unit distance causes counterclockwise turning of the print element 11 by a distance equal to the spacing between adjacent vertical rows of the characters formed on the print element.

The coil spring 27 acting through spring arbor 17, clutch spring 19 and rotate pulley 24 maintains a tension on tape 30 and tends to swing the upper end of rotate arm 32 to the right from the position shown in FIGURES 1 and 2 of the drawings. This places a tension on rotate link 41 tending to rotate the bellcrank 42 in a clockwise direction. Bellcrank 42, acting through balance lever 44, tends to raise the link 53 from the position shown. Link 53 is normally latched in its lower position but may be unlatched so it follows a cam, not shown, to move to its raised position. When the link 53 is moved to its raised position, the rotate bellcrank 42 rocks clockwise a distance of five units, the pulley 31 moves to the right and the print element 11 turns clockwise by a distance corresponding to five units. If the selecting links 46, 47 and 52 are actuated simultaneously with the lifting of link 53, the rotate bellcrank 42 rocks clockwise a distance corresponding to five units minus the counterclockwise distance obtained by operating the selecting links. From the above discussion, it is apparent the print element 11 may be turned in both clockwise and counterclockwise directions from a home position by any distance from one to five units upon proper actuation of the selection mechanism 45. The selection mechanism is actuated in response to depression of keylever by a typist or by received signals controlling the operation of solenoids, not shown, as is well known.

The case shift arm 34 mounted at the right of the printing mechanism carries a cam follower roll 56 intermediate its end which engages a case shift cam 57. The case shift cam 57 is rotated in response to case shift signals and causes pivotal movement of the case shift arm about pivot point 58. Lower case characters are formed on one half of the print element and upper case characters are formed on the other half thereof. Clockwise pivotal movement of the case shift arm 34 from the position illustrated in FIGURE 2 of the drawings causes the print element to rotate in a counterclockwise direction through 180 degrees. Upper case characters are then selected for printing upon actuation of the selection mechanism 45. When the case shifting mechanism is not actuated, lower case characters are brought to the printing position upon operation of the selection mechanism. This case shifting mechanism is fully disclosed in the above referenced Patent 2,919,002 and the instruction manual.

Any portion of the selection or case shift mechanism which wears or moves out of adjustment will cause the print element to rotate to a position which is spaced from the desired position during a character selection operation. This will cause the print element to be displaced slightly so the selected characters are offset from the correct printing .position. While detenting means as shown in Patent 2,926,768 is employed to correct slight positioning errors, the inaccuracies and wear in the mechanisms may exceed the correcting ability of the detenting means in at least a portion of the selection operations. The wear compensating apparatus is designed to compensate for at least a portion of the inaccuracies and wear in the mechanisms for rotating the print element when the latter is rotated clockwise by five units and the case shift mechanism has not been actuated As shown in FIGURE 3 of the drawings, a stop plate 60 is adjustably mounted on the rocker plate 16 in relatively fixed relation with respect to the rotational movements of the spring arbor 17, rotate pulley 24 and the print element 11. A tab 61 projects from the lower end of the spring arbor 17 and, as will be later explained, is adapted to engage the stop plate 60 when the print element moves clockwise by five units as a lower case character is selected. Initially, the stop plate 60 is adjusted so the tab 61 engages the same when the print element has rotated five units clockwise and the case shift mechanism has not been actuated.

The spring clutch 19 is so designed that with the rotate spring 27 exerting a clockwise biasing force on the spring arbor 17 and the rotate tape 30 exerting a reactive counterclockwise pulling force on rotate pulley 24, the convolutions of the spring clutch 19 tightly engage the spring arbor 17 and the rotate pulley 24. With this condition existing, any movement of the rotate tape 30 will produce a like movement of the print element 11 since the rotate pulley 24 and spring arbor 17 are effectively rigidly coupled. During a character selection or case shift operation when the rotate tape 30 pulls on the rotate pulley 24, the windings of the spring clutch 19 tightly engage the rotate pulley and the spring arbor. The rotate pulley 24 moves in a counterclockwise direction against the action of the coil spring 27 and this movement is transmitted through the spring clutch 19 to the spring arbor 17, spindle 12 and print element 11. When the pulley 31 or case shift pulley 33 moves inwardly during a character selection or case shift operation, the coil spring 27 biases the clutch spring 19 into tight engagement with the spring arbor 17 and rotate pulley 24. The coil spring 27 moves rotate pulley 24, spring arbor 17, spindle 12 and print element 11 .in a clockwise direction by a distance corresponding to the movement of pulley 31 or case shift pulley 33.

As the machine is used, wear and changes in the adjustment of any part or portion of the rotate selection mechanism or the case shift mechanism allow the coil spring 27 to move the rotate pulley 24 more and more in the clockwise direction during at least a portion of the selection operations. Under such wearing conditions, the tab 61 of the spring arbor 17 engages stop plate 60 when a clockwise rotation of five units is selected and the case shift mechanism is not actuated. One of the opposing forces on the spring clutch 19 is removed and the convolutions on the spring clutch 19 unwind slightly to release the rotate pulley 24. The print element is maintained in the proper selection position since the coil spring 27 biases the projecting tab 61 of the spring arbor 17 against the adjustable stop plate 60. The rotate pulley 24 is effectively disconnected and can rotate independently with respect to spindle 12 and print element 11 since the hub 23 is not tightly engaged by the spring clutch 19.

A relatively light helper coil spring 62 is connected between the spindle 12 and the rotate pulley 24 as shown in FIGURE 3 of the drawings. The helper spring 62 biases the rotate pulley for clockwise movement but is ineffective at all times except during wear compensating ope-rations since the spring clutch 19 normally connects the spring arbor 17 and rotate pulley 24. The helper spring 62 is strong enough to overcome the frictional forces in the mechanisms and between'the convolutions of the spring clutch 19 and the rotate pulley 24 to rotate this pulley clockwise until all slack in the rotate tape is taken up. As the selection mechanism 45 is de-energized and the spring arbor 17 begins to rotate counterclockwise from the selected position toward the home position, the tab 61 moves from stop plate and spring clutch 19 engages hub 23 of rotate pulley 24 at an adjusted position. The print element 11 is returned to the home position and an automatic adjustment operation to compensate for inaccuracies and wear is completed.

In essence, the wear compensating apparatus comprises a clutch means for drivingly interconnecting the print element with the selection and case shift mechanisms until a wear compensating adjustment is made. The rotate pulley 24 and spring arbor 17 are drivingly connected at all times except during the middle of a particular seleciton cycle. It is noted that the adjustable stop plate 60 does not interfere with selection or case shift operations since slightly less than one complete revolution of the print element 11 is required to position any selected character in a printing position. If desired, a check pawl or detent means may be incorporated so that external rotational forces exerted on the print element 11 or spindle 12, such as when the print element is being removed or replaced, cannot alter the adjusted positional relation between the spring arbor and the rotate pulley.

The disclosed mechanism can be modified by placing the coil spring 27 in a position to bias the rotate pulley 24 rather than the spring arbor 17. The operation is generally the same with the exception that the frictional engagement between the coils of the spring clutch 19 and the spring arbor 17 are relied upon when the rotate pulley moves clockwise. This arrangement has the disadvantage of requiring relatively close tolerances on the force exerted by the coil spring. However, the provision of a check pawl or detent means to prevent misalignment of the parts when external forces are applied to the print element or spindle will obviate this disadvantage.

As mentioned above, characters are formed in vertically spaced circumferentially extending rows on the print element. The printing mechanism comprises mechanism for tilting the print element in response to character selection signals to select a circumferentially. extending row of characters. This tilt selection mechanism has not been described or particularly shown in the present disclosure 7 but is fully explained in the above-identified patent and instruction manual. If desired, wear compensating apparatus of type herein described can be incorporated in this tilt selection mechanism.

It should now be apparent that the objects initially set forth have been accomplished. Of particular importance is the provision of wear compensating apparatus which automatically compensates for a greater portion of the inaccuracies and wear in mechanism employed for positioning a driven member and which apparatus is highly simplified in construction and operation. The teachings of the present invention, while being particularly applicable to printing mechanisms of the type described, can be employed any place wear and inaccuracies are encountered in mechanisms positioning a movable member.

While the invention has been particularly shown and described with reference to a preferred embodiment 7 thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. Apparatus for compensating for wear or the like in at least one mechanism operable to control movement of a movable member having spaced elements thereon to selectively position the elements at a working position comprising:

a movable member having spaced elements thereon and a member driven by said mechanism;

said mechanism operating to move said driven member in both rotational directions;

clutch means drivingly interconnecting and directly coupling said driven member and said movable member for oscillatory movement through a working position to a number of preselected positions when said clutch is engaged;

said clutch means comprising a spring clutch whose convolutions are disposed to normally engage said movable member and said driven member;

means to release said clutch means each time said driven member and said movable member are moved in coupled relation to at least one of said preeselected positions to position an associated one of said elements at said working position; and

means connected with one of said members operable to efiect relative movement between said members when said clutch means is released to compensate for wear and the like in said mechanism.

2. Apparatus for compensating for wear and the like in at least one mechanism operable to control movement of a print element from a home position comprising:

a print element having a plurality of spaced characters disposed about the periphery thereof;

a spindle mounting said print element for rotational movements in both rotational direction;

a rotate pulley mounted for rotation;

a flexible rotate tape attached to and extending at least partially about said rotate pulley; at least one mechanism operating on said tape to pull and release the same to cause rota-tion of said rotate pulley;

a bi-directional clutch means interconnecting said rotate pulley and said spindle whereby rotational movements of said rotate pulley in both rotational directions causes like rotational movements of said print element from its home position;

said bi-directional clutch means comprising a spring clutch having convolutions disposed to engage axially aligned adjacent portions of said rotate pulley and said spindle;

means to release said clutch means when said rotate pulley and said print element are in at least one predetermined rotational position; and

means connected with said rotate pulley operable to efiect relative movement between said rotate pulley and print element when said clutch means is released to compensate for wear and the like in said mechanism.

3. Apparatus according to claim 2 further characterized by:

said means to release said clutch means comprising a relatively stationary stop member and tab projecting from said spindle;

said tab engaging said stop member when said print element and said rotate pulley are in said at least one predetermined rotational position; and

means to eifect relative adjustment movement between said tab and stop member to change said at least one predetermined rotational position.

References Cited by the Examiner UNITED STATES PATENTS 1,865,772 5/1932 Lyman 192-111 X 1,909,420 5/ 1933 Palmgren. 2,360,187 10/ 1944 Almen. 2,989,166 6/1961 Walker et a1 197-16 3,133,620 5/1964 Okcuoglu et a1.

DAVID KLEIN, Primary Examiner.

ROBERT E. PULFREY, Examiner. 

1. APPARATUS FOR COMPENSATING TO WEAR OR THE LIKE IN AT LEAST ONE MECHANISM FOR OPERABLE TO CONTROL MOVEMENT OF A MOVABLE MEMBER HAVING SPACED ELEMENTS THEREON TO SELECTIVELY POSITION THE ELEMENTS AT A WORKING POSITION COMPRISING: A MOVABLE MEMBER HAVING SPACED ELEMENTS THEREON AND A MEMBER DRIVEN BY SAID MECHANISM; SAID MECHANISM OPERATING TO MOVE SAID DRIVEN MEMBER IN BOTH ROTATIONAL DIRECTIONS; CLUTCH MEANS DRIVINGLY INTERCONNECTING AND DIRECTLY COUPLING SAID DRIKVEN MEMBER AND SAID MOVABLE MEMBER FOR OSCILLATORY MOVEMENT THROUGH A WORKING POSITION TO A NUMBER OF PRESELECTED POSITIONS WHEN SAID CLUTCH IS ENGAGED; SAID CLUTCH MEANS COMPRISING A SPRING CLUTCH WHOSE CONVOLUTIONS ARE DISPOSED TO NORMALLY ENGAGE SAID MOVABLE MEMBER AND SAID DRIVEN MEMBER; 